The present invention relates to the sphere of high-pressure pipes intended to equip an oil well or an oil drilling and/or production installation, notably offshore.
Oil is produced from an offshore reservoir using a pipe generally referred to as riser, which allows the wellhead installed at the sea bottom to be connected to the sea surface. The riser is an extension of the tubing carrying the oil from the well bottom to the wellhead. The riser is provided with at least two auxiliary lines called kill line and choke line, whose main function is to establish a hydraulic connection between the sea surface and the wellhead at the sea bottom. More particularly, these auxiliary lines allow to supply the well with fluid by circulating below the closed blowout preventer, and/or to discharge a fluid from the well, without passing through the inside of the riser. The fluid conveyed, resulting from an influx in an underground reservoir, can circulate at a pressure of 700 bars.
In general, the auxiliary lines and the riser are each made from an assembly of tube elements. In order to minimize the number of connections on a riser, the greatest possible tube element length is selected. However, tube handling operations, notably upon mounting an d dismantling of the riser, require limitation of the tubes length to an interval ranging between about 20 and 30 metres. In order to be able to readily and simultaneously carry out mounting of the riser and of the auxiliary lines, the length of the tubes that make up the auxiliary lines is substantially equal to the length of the tubes that make up the riser, i.e. a length ranging between about 20 and 30 metres.
The present invention proposes making auxiliary lines from a pipe element assembly consisting of hooped tubes so as to reduce the weight to which the riser is subjected. However, hooping of an at least 20-m long pipe element requires bulky, sophisticated and therefore expensive machines.
The present invention therefore proposes making an auxiliary line element from an assembly of several hooped tube sections, each pipe element having a length approximately greater than or equal to 20 metres. In particular, the invention provides an embodiment for connection means between the hooped tube sections allowing to obtain an approximately 20-m long pipe element.
The present invention thus relates to a high-pressure pipe element comprising at least two hooped tube sections connected by connection means that meet the mechanical strength and pressure resistance requirements relative to a hooped tube section.
The connection means can comprise an intermediate part screwed between the two sections, seal means, locking means for fastening the sections on said intermediate part.
The intermediate connecting part can be a tube whose outside diameter is smaller than or at most equal to the outside diameter of the hooped tube sections.
The locking means comprise at least one U-shaped part intended to block any longitudinal play between the sections and the intermediate part. Each edge of the U-shaped part can be inserted in a groove machined around each end of a hooped tube section, and the U can be fastened to the intermediate connecting part by the bottom of the U.
The pipe element according to the present invention can consist of four approximately 4-m long sections and of two approximately 2.5-m long sections.
The pipe element according to the present invention can be used to make an auxiliary line of a drilling riser, and the auxiliary line can be a kill line, a choke line, a booster line or a mud return line.